1. Field of the Invention
The present invention relates to an auxiliary information generation method, an auxiliary information generation apparatus, an image data generation method, and a data storage medium. More particularly, the invention relates to a method and an apparatus for generating auxiliary information which is used as index information when extracting or selecting a part of digital data such as digital video and audio data, and a method for generating partial video data by extracting a desired portion of image data by utilizing the auxiliary information, as well as a method and an apparatus for playing the partial video. Further, the invention relates to a data storage medium which stores a program for making a computer execute the auxiliary information generation method and the video data generation method, and data generated as the result of executing these methods.
2. Description of the Related Art
In recent years, with the progress in digitization of video and audio, standardization of video and audio data compression methods such as MPEG-2 and MPEG-4 has been achieved for the purpose of improving efficiency in recording or transmission and, furthermore, standardization relating to description of auxiliary information, which is used when selecting desired data from a database holding these video and audio data or extracting a portion of the video data, has been promoted as MPEG-7.
Hereinafter, an example of description of auxiliary information relating to digital data based on MPEG-7 will be described with reference to drawings (ISO/IEC JTC 1/SC 29/WG 11/N3411, “MPEG-7 Multimedia Description Schemes WD (Version 3.0)”, 2000.5).
As for viewing of video and audio data, it has been common practice that contents of video and audio data produced by a producer are broadcast and viewed by many people. However, as mobile devices such as personal computers and handy phones have become widespread, these mobile devices have permitted the users to interactively operate video and audio data through the Internet or the like, as well as to view these data one-sidedly. Accordingly, it is expected that service patterns, which enable the users to retrieve only a desired portion of contents from databases scattered on the Internet without viewing all of the contents, or enable the providers to select contents according to preferences of the users and distribute the contents to the users, will become widespread in the future. MPEG-7 is an international standard, which is now under standardization, for describing temporal information, contents, preferences of users, and the like with respect to multimedia data such as video and audio.
FIG. 50 shows an example of description based on MPEG-7 (excerpt from ISO/IEC JTC 1/SC 29/WG 11/N3410, “MPEG-7 Multimedia Description Schemes XM (Version 3.0)”, 2000.5). In this example, a portion of video data is described by a description of VideoSegment, and the VideoSegment corresponds to one scene. Auxiliary information is described by using MediaTimePoint indicating the start time of this segment, MediaDuration indicating the duration of this segment, and SegmentDecomposition indicating the presence or absence of a gap between segments, and the like. As shown in FIG. 51, this auxiliary information 3003 is added to a header 3002 or the like of video data 3000, whereby the user can easily search for or extract desired data such as video data. In FIG. 51, 3001 denotes a data body corresponding to the video data 3000 excluding the header 1002.
In MPEG-7, however, only the description itself of the auxiliary information relating to contents information is standardized, and a method for generating the auxiliary information is not defined. Further, there is no definition about what kind of information is to be provided using MPEG-7.
Meanwhile, with respect to mobile devices such as handy phones which have rapidly become widespread or progressed in functions, it is expected that those provided with capturing functions such as cameras or movies will become inexpensive in the future. In this case, a captured (moving) picture can be transmitted to a destination through a mobile communication network. On the other hand, the telephone charge on such video communication is not necessarily a fixed charge such as a month-by-month basis. In the case of mobile terminals, a pay-per-view basis according to the amount of transmitted/received data is usually employed. Therefore, if the whole of a captured (moving) picture is transmitted as it is, the communication cost will become high.